John Lansdale, Jr.
The Manhattan Project was probably the best kept secret of World War II. General Leslie Groves, the project's director, selected John Lansdale, Jr. as head of security. Lansdale, a highly intelligent and capable lieutenant colonel, earned his undergraduate degree at the Virginia Military Institute and was later awarded a degree in law from Harvard. He worked well with Groves claiming, "Most of us working with him performed better than our intrinsic abilities indicated."
Though Lansdale did not serve at Los Alamos, he was charged with ensuring the laboratory's security. He was well suited for the task. In addition to his acumen and uncommon ability to work well with Groves, Lansdale had already gained experience in conducting investigations of potential subversives for the army's Military Intelligence Division. In early 1942, James B. Conant hired Lansdale to investigate Ernest Lawrence's laboratory at Berkeley. Lansdale found security considerations to be so lacking, that by the end of his fortnight on campus he had learned about virtually every aspect of the cyclotron project. Impressed by Lansdale's work, Groves recruited Lansdale in September.
By early 1943, Lansdale had established branch intelligence offices at all the Manhattan Project's installations. During this time, he also conducted a background check of J. Robert Oppenheimer. Although he suspected Oppenheimer's wife, brother, and sister-in-law were communists, he concluded Oppenheimer himself posed no threat. Years later, he would defend his conclusions before Congress at the height of the red scare.
As the project was getting underway, Lansdale formed the ALSOS mission. ALSOS was formed to gather intelligence on German nuclear developments. As the war came to a close in Europe, ALSOS collected information on and actual materials from the German nuclear project. Agents also apprehended several of the project's leaders, including Otto Hahn and Werner Heisenberg.
The ALSOS mission was a complete success. No less successful were Lansdale's efforts to maintain the secrecy of Project Y. Considering the colossal scale of the project, it was a magnificent achievement.